FRP road bridges as a concrete alternative : determining life cycle costs of all-FRP and concrete road bridges using a parametric calculation tool

Transport infrastructure is of great economic value because it allows trade, which is essential to the
development of societies. Infrastructure owners have the responsibility to ensure the correct functioning of
infrastructure. They self-evidently search for a way to ensure this correct functioning of infrastructure while
simultaneously aspiring to have the lowest costs that accompany this responsibility. Increasingly
infrastructure owners turn to infrastructure asset management to cope with this problem. Infrastructure
asset management is a systematic approach to manage infrastructure assets cost-effectively. One aspect of
infrastructure asset management is life cycle cost (LCC) analysis. With life cycle cost analysis investment
decisions can be made based on the total cost incurred during the complete life cycle of an asset.
This research focuses on the life cycle costs of bridges. Alternative bridge designs offer alternative
investment possibilities. Currently bridge decks are often build with reinforced concrete, but fiber reinforced
polymer (FRP) is emerging as an alternative construction material for bridge decks. Claims are made that
FRP bridges can offer financial and environmental benefits as a construction material. However, in practice
it is unclear in what situations and to what extent FRP offers these benefits. This causes engineers to be
reluctant with choosing FRP as a bridge deck construction material.
The objective of this research has been to aid engineers in making a more informed decision when choosing
a bridge deck construction material by offering a parametric LCC calculation tool. This tool allows the user
to enter a certain bridge design and maintenance scenario which the tool then uses to calculate the total
LCC.
First, based on literature on LCC an LCC model was developed which describes the input parameters,
necessary calculations and resulting outputs. This led to dividing the total LCC into three cost categories: 1)
Agency costs, costs incurred by the agency (construction, maintenance, end of life); 2) User costs, costs
incurred by the user of the road (delay, vehicle operation, accidents); 3) Society costs, costs incurred by
society as a whole (environmental). Next this model was translated into a calculation tool developed in
spreadsheet software. To test the workings of the tool and to get an idea of the competitiveness of FRP
bridge decks for beam road bridges, a specific case analysis has been performed. Based on the results the
following conclusions have been drawn.
Total LCC values are largely determined by the initial investment costs. This is because the user costs and
maintenance costs - which occur in the future – are discounted and the environmental costs are very small
compared to the other cost categories.
The investment costs of bridge decks make up a large part of the initial investment costs (especially at larger
spans) and therefore make up a large part of the total LCC. The premium price of FRP bridge decks
compared to concrete bridge decks (about twice as high) is therefore hard to negate with lower maintenance
costs and user costs. This becomes even harder as spans increase.
The discount factor used has the largest influence on LCC results, followed by extra travel time caused by
work zones. If maintenance scenarios are different enough between the two design alternatives these two
variables can be decisive for what the preferred design alternative will be at smaller spans.
Overall bridges with FRP bridge decks for beam road bridges have a hard time competing with concrete
bridge decks. At smaller spans (10 to 15 meters) user costs might contribute enough in certain cases to total
LCC to cancel out the premium price of FRP bridge decks. At larger bridge spans this seems unlikely with
current production costs.